This invention relates to building structure components assembled with little or no welding required at the construction site.
Steel structural members may be connected to construct various building structures. Various structural members, for example joists, beams, girders, studs, channels, bridging, decking, clips, brackets, and other components may be connected together to form a structure. Typically, steel structural members have been joined by welding the members together, bolting the members together, or a combination of both.
Welded connections have been effectively used in building structures; however, welding steel structural members together during the erection of a building structure requires a trained welder with welding equipment at the job site to perform the welding. The difficulty of providing welded connections increases with difficult and/or remote conditions of the construction site, and as the size and height of the structure increases.
Steel bolts have been used instead of certain welded connections. A typical prior art connection may include a bolt placed in pre-drilled holes through the components being connected and fastened in place with a nut. To complete a bolted connection, the bolt holes must be aligned sufficiently to pass the bolt through the holes. Then, the bolt must be held while the nut is turned onto the bolt and tightened. Fastening a nut onto the bolt required the installer to have access to both sides of the connection. For large structural members, positioning and holding the members to align the bolt holes has been a disadvantage. Bolted connections have been difficult to complete when the pre-drilled holes are not sufficiently aligned, and extra time and effort was required to set the structural members in place for hole alignment and bolting. Additionally, providing pre-drilled holes in each member increased the number of unique parts on the job site, increasing the amount time required to ensure the proper parts are used in their desired locations.
Another problem in the prior art is securing a plurality of structural members during assembly of certain connections, such as double connections involving two members that share common bolts on either side of a central piece. Federal regulations by the Occupational Safety and Health Administration (OSHA) require that for such double connections the first member must be attached before the second member is connected. This typically requires an extra bolt connection for attaching the first member positioned so as to not interfere with the placement of the second member. The increased complexity of providing pre-drilled holes and complying with OSHA securement requirements has decreased efficiency in producing and installing the structural members.
Self-drilling and self-threading bolts have been used in certain metal connections adjoining different building elements of materials, such as low carbon steel, stainless steel or aluminum. However, prior self-drilling and self-threading bolts were case hardened to provide a desired hardness. The prior case hardened bolts lacked ductility, and the case hardened portion would break when loaded in certain structural connections causing premature fastener failure. Additionally, in connections where the prior self-drilling bolts could be used, additional installation time was required because of the difficulty in driving the bolts. Many fastener installations are made using electric or pneumatic drivers, and for certain applications drivers with rotary impact mechanisms have been used to deliver the torque needed to install certain fasteners. Without impact mechanisms, drivers typically have been limited to smaller fasteners requiring limited torque. Impact mechanisms may be used to drive self-threading fasteners to form threads in the drilled hole in the structural member, and certain prior self-drilling or self-tapping bolts required impact driving to drive the thread portion of the bolt through the threaded member. For longer bolts in the past, impact driving was time consuming and inefficient.
Steel bolts and screws have been tried in certain applications to join sheet metal building members. For example, U.S. Pat. No. 4,982,545 discloses a truss that includes web members and chord members fastened with screws. However, screws and bolts used in the past for sheet metal connections have caused assembly problems such as strip-out that have increased the time for assembly and increased scrap costs. Strip-out occurs when the shape of the hole deforms and/or the hole enlarges such that the threads of the screw cannot engage the material around the hole enough to tighten the screw or bolt. Additionally, the prior self-drilling bolts experienced high rates of tipping or angled installation in sheet metal applications. Strip-out and tipping required rework or additional screws to be installed to achieve the desired connection strength, increasing time and cost of installation. Typical prior art self-drilling screw are shown in FIGS. 3A and 3B for connecting sheet metal components together. The screw has a head, a thread portion having a major diameter and a minor diameter, and a self-drilling tip having a notch or flute. In the past, after the self-drilling tip drilled through the material, the threaded portion would thread into the hole. As the threads typically did not continue to the head, the driving torque had to be controlled to avoid stripping the screw in the hole. These screws were relatively easy to strip in a sheet metal application, causing increased time for assembly and increased scrap costs. Additionally, certain prior fasteners were tailored to perform in a particular substrate thickness, but when the fasteners were used in another material thickness, the fasteners could not obtain the same performance.
What is disclosed is a building structure comprising a first steel building member and a second steel building member connected by a plurality of fasteners, each fastener being steel comprising a head capable of clamping the first steel building member to the second steel building member with the fastener installed, a threaded portion adjacent the head, a thread-forming portion adjacent the threaded portion of at least HRC 50 hardness adapted to form threads into at least the second steel building member, and a fluted lead portion adjacent the thread-forming portion of at least HRC 50 hardness with a nominal diameter in a range from 60% to 95% of major diameter of the threaded portion adapted to form a fastener opening, such that the fastener is capable of providing a ratio of strip torque to thread-forming torque of at least 2.7 and a ratio of strip torque to drive torque greater than 6.0 over a range of combined thickness of first and second steel building members from 0.036 inch to 0.084 inch.
Alternatively, the fasteners may have a ratio of strip torque to thread-forming torque of at least 2.7 and a ratio of strip torque to drive torque greater than 8.0 over a range of combined thickness of first and second steel building members from 0.036 inch to 0.084 inch. In yet another alternative, the fasteners may have a ratio of strip torque to thread-forming torque of at least 2.7 and a ratio of strip torque to drive torque greater than 6.0 over a range of combined thickness of first and second steel building members from 0.036 inch to 0.108 inch. Alternatively, the fasteners may have a ratio of strip torque to thread-forming torque of at least 3.0 and a ratio of strip torque to drive torque greater than 6.0 over a range of combined thickness of first and second steel building members from 0.036 inch to 0.084 inch. In yet another alternative, the fasteners may have a ratio of strip torque to thread-forming torque of at least 3.0 and a ratio of strip torque to drive torque greater than 6.0 over a range of combined thickness of first and second steel building members from 0.036 inch to 0.108 inch. For certain applications, the combined thickness of the first steel building member and the second steel building member at the fastener may be no more than 0.125 inch in thickness. In any case, the fasteners may be nutable.
The fastener threaded portion adjacent the head may have a through hardness in a range from HRB 70 and HRC 40. Additionally, the fasteners may have up to five threads between the threaded portion and the thread-forming portion that are hardened to at least HRC 50 hardness. The threaded portion may have less than 60° thread angle and back-tapered threads. Alternatively, the thread angle may be between 40° and 50°.
In one alternative, threaded portion of the fastener adjacent the head may have a case hardness of at least HRC 50.
The lead portion of the fluted lead portion of the fasteners may include a milled point, and may have at least HRC 50 hardness. The fluted lead portion may be adapted to form a fastener opening with a diameter between 62% and 85% of major diameter of the threaded portion.
The thread-forming portion of the fasteners may have a shape selected from a group consisting of quadlobular and pentalobular. The thread-forming portion may be from 3 to 7 thread pitch in length.
The fastener threaded portion may extend to adjacent the head of the fastener. Additionally, a sealing member may be positioned between the head and the threaded portion. The head of the fastener may be undercut and adapted to deform the first steel building member on tightening of the fastener. In alternatives in which the head is undercut, a sealing member may optionally be positioned adjacent the undercut. Alternatively or additionally, the threaded portion may comprise a major diameter extending to within 1.5 of the thread pitch of the head. Optionally, serrations may be provided in the undercut. In any case, such fasteners have the added advantage of increased back-out resistance and are less likely to come loose by vibration. These undercut fasteners provide an improved shear strength with the present invention between sheets of building materials not previously available with prior art fasteners.
Also disclosed is a building structure comprising a first steel building member and a second steel building member connected by a plurality of fasteners, each fastener being steel comprising a head capable of clamping the first steel building member to the second steel building member with the fastener installed, a threaded portion adjacent the head, a thread-forming portion adjacent the threaded portion of at least HRC 50 hardness adapted to form threads into at least the second steel building member, and a fluted lead portion adjacent the thread-forming portion of at least HRC 50 hardness with a nominal diameter in a range from 60% to 95% of major diameter of the threaded portion adapted to form a fastener opening, such that the fastener is capable of providing a ratio of strip torque to thread-forming torque of at least 3.5 and a ratio of strip torque to drive torque greater than 8.0 over a range of combined thickness of first and second steel building members from 0.054 inch to 0.084 inch.
Alternatively, the fasteners may provide a ratio of strip torque to thread-forming torque of at least 3.5 and a ratio of strip torque to drive torque greater than 10.0 over a range of combined thickness of first and second steel building members from 0.054 inch to 0.084 inch. Alternatively, the fasteners may have a ratio of strip torque to thread-forming torque of at least 3.5 and a ratio of strip torque to drive torque greater than 6.0 over a range of combined thickness of first and second steel building members from 0.036 inch to 0.084 inch. In yet another alternative, the ratio of strip torque to thread-forming torque may be at least 3.5 and a ratio of strip torque to drive torque greater than 8.0 over a range of combined thickness of first and second steel building members from 0.036 inch to 0.084 inch. Alternatively, the fasteners may provide a ratio of strip torque to thread-forming torque of at least 4.0 and a ratio of strip torque to drive torque greater than 8.0 over a range of combined thickness of first and second steel building members from 0.054 inch to 0.084 inch. Alternatively, the ratio of strip torque to thread-forming torque may be at least 3.0 and a ratio of strip torque to drive torque greater than 4.0 over a range of combined thickness of first and second steel building members from 0.036 inch to 0.108 inch. For certain applications, the combined thickness of the first steel building member and the second steel building member at the fastener may be no more than 0.125 inch in thickness. In any case, the fasteners may be nutable.
The fastener threaded portion adjacent the head may have a through hardness in a range from HRB 70 and HRC 40. Additionally, the fasteners may have up to five threads between the threaded portion and the thread-forming portion that are hardened to at least HRC 50 hardness. The threaded portion may have less than 60° thread angle and back-tapered threads. Alternatively, the thread angle may be between 40° and 50°.
In one alternative, threaded portion of the fastener adjacent the head may have a case hardness of at least HRC 50.
The lead portion of the fluted lead portion of the fasteners may include a milled point, and may have at least HRC 50 hardness. The fluted lead portion may be adapted to form a fastener opening with a diameter between 62% and 85% of major diameter of the threaded portion.
The thread-forming portion of the fasteners may have a shape selected from a group consisting of quadlobular and pentalobular. The thread-forming portion may be from 3 to 7 thread pitch in length.
The fastener threaded portion may extend to adjacent the head of the fastener. Additionally, a sealing member may be positioned between the head and the threaded portion. The head of the fastener may be undercut and adapted to deform the first steel building member on tightening of the fastener. In alternatives in which the head is undercut, a sealing member may optionally be positioned adjacent the undercut. Alternatively or additionally, the threaded portion may comprise a major diameter extending to within 1.5 of the thread pitch of the head. Optionally, serrations may be provided in the undercut. In any case, such fasteners have the added advantage of increased back-out resistance and are less likely to come loose by vibration.
In one alternative, the building structure may comprise a first steel building member and a second steel building member connected by a plurality of fasteners, each fastener being steel comprising a head capable of clamping the first steel building member to the second steel building member with the fastener installed, a threaded portion adjacent the head having a through hardness in a range from HRB 70 to HRC 40, a thread-forming portion adjacent the threaded portion of at least HRC 50 hardness adapted to form threads in at least the second steel building member, and a fluted lead portion adjacent the thread-forming portion of at least HRC 50 hardness with a nominal diameter in a range from 75% to 95% of major diameter of the threaded portion adapted to form a fastener opening, such that the fastener is capable of providing a ratio of failure torque to thread-forming torque of at least 2.7 and a ratio of failure torque to drive torque greater than 6.0 over a range of combined thickness of first and second steel building members from 0.10 inch to 0.47 inch.
Alternatively, the fasteners may be capable of providing a ratio of failure torque to thread-forming torque of at least 3.0. In yet another alternative, the fasteners may be capable of providing a ratio of failure torque to thread-forming torque of at least 3.75. The fasteners may have a drive torque no more than 50% of a thread-forming torque. The fasteners may be nutable.
The lead portion of the fluted lead portion of the fasteners may have a milled point, and may have at least HRC 50 hardness.
The fastener thread-forming portion may have a shape selected from a group consisting of quadlobular, pentalobular and hexalobular. The thread-forming portion may be from 3 to 7 thread pitch in length.
Additionally, the fasteners may have up to five threads between the threaded portion and the thread-forming portion that are hardened to at least HRC 50 hardness. The threaded portion may have less than 60° thread angle and back-tapered threads. Alternatively, the thread angle may be between 40° and 50°.
Also disclosed is a building structure comprising a first steel building member and a second steel building member connected by a plurality of fasteners, each fastener being steel comprising a head capable of clamping the first steel building member to the second steel building member with the fastener installed, a threaded portion adjacent the head having a through hardness in a range from HRB 70 to HRC 40, a thread-forming portion adjacent the threaded portion of at least HRC 50 hardness adapted to form threads in at least the second steel building member, and a fluted lead portion adjacent the thread-forming portion of at least HRC 50 hardness with a nominal diameter in a range from 80 to 92% of major diameter of the threaded portion adapted to form a fastener opening, such that the fastener is such that the fastener is capable of providing a ratio of failure torque to thread-forming torque of at least 3.0 and a ratio of failure torque to drive torque greater than 10 when the second steel building member having a thickness of 0.25 inch.
Alternatively, the fasteners may be capable of providing a ratio of failure torque to thread-forming torque of at least 3.0 and a ratio of failure torque to drive torque greater than 10 over a range of second steel building member thickness from 0.25 inch to 0.47 inch. The fasteners may have a drive torque no more than 50% of a thread-forming torque. The fasteners may be nutable.
The lead portion of the fluted lead portion of the fasteners may have a milled point, and may have at least HRC 50 hardness.
The fastener thread-forming portion may have a shape selected from a group consisting of quadlobular, pentalobular and hexalobular. The thread-forming portion may be from 3 to 7 thread pitch in length.
Additionally, the fasteners may have up to five threads between the threaded portion and the thread-forming portion that are hardened to at least HRC 50 hardness. The threaded portion may have less than 60° thread angle and back-tapered threads. Alternatively, the thread angle may be between 40° and 50°.
At least a portion of the threaded portion of the fastener may meet a specification selected from a group consisting of ASTM A307, ASTM A325, ASTM A354, and ASTM A490 specifications. Alternatively or in addition, at least a portion of the threaded portion of the fastener may meet a specification selected from a group consisting of SAE J429 Grade 2, SAE J429 Grade 5, and SAE J429 Grade 8.
Alternatively, a building structure may comprise a first steel building member and a second steel building member connected by a plurality of fasteners, each fastener being steel comprising a head capable of clamping the first steel building member to the second steel building member with the fastener installed, a tapered lead portion having an angle in the range from 30 to 60° of at least HRC 50 hardness adapted to start into a pilot hole in at least the second steel building member, a thread-forming portion of at least HRC 50 hardness adapted to thread the fastener into at least the second steel building member, and a threaded portion having a through hardness of in a range from about HRB 70 to HRC 40, such that the fastener and capable of providing a ratio of failure torque to thread-forming torque of at least 3.0 and a ratio of failure torque to drive torque greater than 10 when the second steel building member having a thickness of 0.25 inch and the pilot hole having at least one diameter within nominal diameter from 80 to 98% of major diameter.
The fasteners may have a drive torque no more than 50% of a thread-forming torque. The fasteners may be nutable.
The tapered lead portion of the fasteners may have at least HRC 50 induction hardness.
The fastener thread-forming portion may have a shape selected from a group consisting of quadlobular, pentalobular and hexalobular. The thread-forming portion may be from 3 to 7 thread pitch in length.
Additionally, the fasteners may have up to five threads between the threaded portion and the thread-forming portion that are hardened to at least HRC 50 hardness. The threaded portion may have less than 60° thread angle and back-tapered threads. Alternatively, the thread angle may be between 40° and 50°.
At least a portion of the threaded portion of the fastener may meet a specification selected from a group consisting of ASTM A307, ASTM A325, ASTM A354, and ASTM A490 specifications. Alternatively or in addition, at least a portion of the threaded portion of the fastener may meet a specification selected from a group consisting of SAE J429 Grade 2, SAE J429 Grade 5, and SAE J429 Grade 8.
Also described is a method of connecting a plurality of members in a building connection comprising providing a first building member having a first mounting surface and a second mounting surface opposite the first mounting surface and a first member thickness there between, providing at least one fastener having a thread-forming portion and a threaded portion, positioning a second building member having a first aperture adjacent the first mounting surface, installing the fastener through the first aperture and forming threads in a fastener opening through the first member thickness connecting the second member to the first member with the thread-forming portion extending through the second mounting surface, positioning a third building member having a second aperture larger than the major diameter of the threaded portion adjacent the second mounting surface such that the second aperture is positioned over the threaded portion, and installing a nut over the threaded portion to connect the third member to the first member.
The step of providing at least one fastener may include providing a steel fastener comprising a head capable of clamping the second building member to the first mounting surface with the fastener installed, a threaded portion adjacent the head having a through hardness in a range from HRB 70 to HRC 40, a thread-forming portion adjacent the threaded portion of at least HRC 50 hardness adapted to form threads in the fastener opening, and a fluted lead portion adjacent the thread-forming portion of at least HRC 50 hardness with a nominal diameter in a range from 80 to 98% of major diameter of the threaded portion adapted to form the fastener opening, such that the fastener is nutable and capable of providing a ratio of failure torque to thread-forming torque of at least 2.7 when the first member thickness is 0.25 inch.
Additionally, the method may further include after the step of providing a first member, providing the fastener opening through the first member thickness, and where the step of providing at least one fastener comprises providing a steel fastener comprising a head capable of clamping the second building member to the first mounting surface with the fastener installed, a tapered lead portion having an angle from 30 to 60° of at least HRC 50 hardness adapted to start into the fastener opening in the first member thickness, a thread-forming portion of at least HRC 50 hardness adapted to thread the fastener into the fastener opening, and a threaded portion having a through hardness of in a range from about HRB 70 to HRC 40, such that the fastener is nutable and capable of providing a ratio of failure torque to thread-forming torque of at least 3.0 when the first member thickness is 0.25 inch and the fastener opening having at least one diameter within nominal diameter in a range from 80 to 98% of major diameter.